This could be one of several reasons.
The battery is in:-
Near the top of the state of charge range (80-100%) the maximum battery charge power is reduced to preserve battery life.
For cold or warm temperatures the battery will limit its charge & discharge power.
Duracell normal operating range is 20C - 40C.
SolaX X1 AC operating range is 5 - 45C
Optimisation service may be limiting the amount of PV absorbed to ensure the battery is available for other, higher paying grid trading services.
For technical support for your battery please contact email@example.com